A typical router has two functions: a routing function and forwarding function. The routing function entails sending, receiving, and processing messages under different routing protocols (e.g., Border Gateway Protocol (BGP), Intermediate-System to Intermediate-System (IS-IS) protocol, Open Shortest Path First (OSPF) protocol, etc.), to obtain and store information, about different paths from local routers to reachable destinations. The router stores the information in a route information base (RIB). The router uses the RIB to collect, in a forwarding information base (FIB), information for selecting best paths for the reachable destinations.
The forwarding function entails receiving and forwarding packets toward their destinations in accordance with the FIB.